1. Field of the Invention
This invention relates to slide fasteners and, in particular, to improvements in what may be termed a semi-automatic lock slider which can be locked against movement in a desired position on rows of interlocking fastener elements of the discrete type by turning a pull tab to a predetermined recumbent position on the slider body.
2. Description of the Prior Art
According to a lock slider of the type under consideration, at least one fastener element within the slider body is cammed into a depression formed in the inside surface of the bottom wing or plate member of the slider body when a pull tab is manually turned to a recumbent position thereon. The slider is intended to stay locked on the rows of fastener elements as long as the pull tab is maintained in the recumbent position.
The depression in the bottom wing of the slider body has conventionally been of such shape, however, that the fastener element engaged therein is comparatively easy to be disengaged therefrom as the pair of fastener stringers are subjected to a pull tending to separate them away from each other, even if the pull tab remains in the recumbent position. The conventional lock slider is thus likely to be unlocked accidentally as the successive fastener elements move into and out of the depression with the continued exertion of such a pull on the fastener stringers.